Cambridge Philosophical Society. 75 



been graduall}' introduced throughout our navy, and were fully 

 described and illustrated by Mr. Brockedon, who made great use 

 of drawings and models for the purpose. They consist essentially 

 in using rolled iron in the form of plates, so placed that the strain 

 shall be in the direction of their depth ; and also in giving greater 

 depth to the anchor as a whole, in the direction of the line of re- 

 sistance. By these means anchors containing a certain weight of 

 metal have, when opposed to much heavier anchors of the usual 

 form, torn them to pieces. These improvements have all been 

 patented, and also described elsewhere, so that it will be unneces- 

 sary to report more fully on them here. 



June 1. — Mr. Faraday entered into an account of the principle 

 of that most perfect of locks invented by the late Mr. Bramah, and 

 of the apparatus belonging to Mr. Mordan, by which they are con- 

 structed. The apparatus (from Mr. Mordan's works) were in the 

 room, their principles explained, and their efficacy and perfection 

 illustrated by the performance of the various processes to which 

 each was devoted. 



June 8. — Mr. Edwards gave a full detail of the recent important 

 improvements in lithotrity by Baron Heurteloup. He prefaced it 

 by an account of the structure of the parts concerned, and of what 

 others had done in this branch of medical science ; after which he 

 reviewed the instruments successively invented by Baron Heurte- 

 loup ; and especially dwelt on the last, an instrument by which 

 the calculus is seized, and then crushed and broken by blows of a 

 hammer from the outside, without any distress to the patient. Baron 

 Heurteloup himself, after the lecture, illustrated the mode of ope- 

 ration, upon real calculi, fully demonstrating the power and rapidity 

 of operation of the instrument. 



This was the concluding evening of the meetings for the present 

 season. 



CAMBRIDGE PHILOSOPHICAL SOCIETY. 



March 5, 1832. — The President (Prof. Sedgwick) in the chair. 

 Among the presents were; a collection of British Insects from 

 A. Badger, Esq. Trinity College, and a specimen of the Northern 

 Diver, from Dr. Butler. , 



A paper was read " On a new analyser, and its use in experi- 

 ments of polarization," by Prof. Airy. — The author mentioned this 

 as an instance in which results deduced from Fresnel's theory had 

 been confirmed by observation, and which therefore served to esta- 

 blish the correctness of that theory. The experiments were sug- 

 gested by a consideration of the theoretical use of the analysing 

 plate in the ordinary polarizing apparatus. The light which falls 

 upon a crystalline plate has upon emerging from it the same in- 

 tensity (neglecting the loss of light at the surfaces, &c.) as before 

 it entered ; and consequentl}' no coloured rings can be seen. By 

 the use of an analysing plate, coloured rijigs arc seen in experi- 

 ment ; and the theoretical explanation of this is, that the analyser has 

 resolved the light that emeri^cs from the crystal into two streams of 



L2 



